1. Field of the Invention
This invention relates to a method for controlling a reproduction process, and in particular, to a method for controlling an electrophotographic copying process thereby allowing to maintain the copying characteristics at constant in spite of occurrence of changes in operating conditions.
2. Description of the Prior Art
In an electrophotographic copying process, use is usually made of a photosensitive member comprised of a photoconductive material which changes its characteristics depending upon temperature. One of the main temperature depending characteristics is the so-called gamma characteristic which relates to the potential of an electrostatic latent image formed on the photosensitive member. Such changes in the gamma characteristic are undesirable because they will adversely affect the quality of a resulting copy image. In general, the temperature inside a copying machine increases as the copying machine is used for an extended period of time. For example, in a cold district, such a temperature increase inside a copying machine is often found to range between 20.degree. and 30.degree. C. Accordingly, the temperature of the photosensitive member also increases by 20.degree.-30.degree. C. Under the circumstances, it is necessary to control a copying process suitably so as to allow to obtain copy images of uniform and excellent quality despite of temperature changes in the photosensitive member.
In accordance with a typical prior art copying process control method, a reference temperature is determined from a photosensitive member to be used and at the same time reference operating conditions for process variables such as the amount of uniform charging, the amount of exposure and the level of developing bias voltage are predetermined in consideration of the reference temperature. One or more of such process variables are selected and the thus selected process variables are varied depending upon the difference between the current temperature of the photosensitive member and the reference temperature by detecting the temperature of the photosensitive member. However, such a prior art approach is not always satisfactory partly because the process variables to be changed depending upon temperature changes of the photosensitive member are fixed and temperature-dependent characteristic changes of a photosensitive member involve a rather complicated mechanism.